Biological instincts come to the fore during Prime Minister's Questions in the House of Commons. Photograph: PA

About a year after being appointed speaker of the House of Commons, John Bercow announced that he wanted to reform the traditionally abrasive weekly prime minister's questions to foster more civilised debate. But new research from the University of Nebraska on the psychology of political persuasions suggests that confrontation between the political right and left is here to stay.

The research published online last week by the Royal Society indicates that where you put your cross on the ballot paper on polling day is, at least in part, instinctive. In other words, socialists and conservatives may be born not made.

Emotions in mammals are fuelled by the brain's evolutionarily ancient "appetitive" (desire for food and attachment) and "aversive" (defensive) systems. The appetitive system promotes social cohesion whereas aversive mechanisms drive autonomous survival. These mechanisms can be categorised as approach or avoidant responses: we approach what gives us pleasure (such as food or social contact) and we avoid things we know will harm us (such as faeces or predators).

We are all found somewhere on the approach-avoidant spectrum. Highly social people enjoy novel experiences and meeting strangers and will have a higher than average approach score, whereas others may feel aggression, suspicion and anxiety when confronted with surprises and strangers.

The new research suggests that these physiological and cognitive variations are likely to correlate with political preference. The study found that people at the appetitive end of the spectrum are more likely to vote for left-wing parties and want money spent on free public art events, whereas those at the aversive end of the spectrum are more likely to vote conservative and want tighter border controls.

Sex differences are also highlighted by these measures, with females (or males with higher than average levels of empathy) more likely than average males to overcome their feelings of disgust or threat and vote left wing.

The team at the University of Nebraska have undertaken several studies over the past few years examining the relationship between personality and political bias. In the latest study they tested whether right-wing participants experienced relatively increased skin conductance (they sweated more, a measure of psychological or physiological arousal) when viewing aversive images (an open wound, a toilet with faeces on it, someone held at gunpoint or a car accident). They also tested whether left wingers experienced increased relative skin conductance when exposed to appetitive images (a bunny rabbit, puppy, a sunset).

The results showed those with right-wing beliefs had a relatively increased response to disgust and threat, whereas those who vote left-of-centre had a relatively increased response to pleasurable images.

The research team hypothesised that if pictures of famous politicians (Ronald Reagan, Bill Clinton, Hilary Clinton and George W Bush) were shown to their subjects, those who were politically right-of-centre would exhibit a greater aversive reaction to ideologically dissimilar politicians, whereas those who were left-of-centre would exhibit a greater appetitive response (in relative terms) when viewing left-of-centre politicians. This was indeed the case.

This suggests that left-wing people are relatively more responsive to appetitive than aversive stimuli and that people who are right-of-centre are more responsive to aversive stimuli. Put another way, conservatives are more responsive to negative stimuli whereas those on the left are more responsive to positive stimuli.

The implication is that the same stimuli will evoke polarised responses depending on where you are on the aversive-appetitive spectrum. These different reactions to shared experiences will mean those of politically opposing viewpoints will automatically judge the other as wrong, and no amount of arguing in the House of Commons can change that.

A further, significant finding from this research is that right-wing people give over more time and increased attention to things they find aversive, in spite of their greater physiological response to those stimuli. For example, a far-right wing person may find homosexuality disgusting and may become angered by the notion of same-sex relationships, but they may devote time to pursuing their object of disgust. This new research suggests the rigidity and intolerance of right-wing people to nonconformity might be vehemently expressed because these people are obsessively intolerant of things they find different and aversive.

High scores in aversive behaviour also correlate with autistic spectrum disorders, narcissism and socio- and psychopathologies. People with a diagnosis along these lines also suffer increased perceptions of threat and sensations of disgust when compared to the average. More men than women exhibit these pathologies.

It should be noted that the research only included participants with ideological convictions – it did not measure the behaviour of floating voters.

The research team hope that a greater social tolerance will emerge from public acceptance that our political outlook is in part biologically determined. Because if our individual cognitive and physiological systems mean we experience the world in fundamentally different ways, this helps to explain why people support different political parties when facing the same social problems.

But this research also suggests that when David Cameron and his ministers sit in the House of Commons and look over at the faces of the opposition they are more likely to experience a sense of threat and disgust than their political rivals do when looking back at them. It is going to be far harder for conservatives to bury the hatchet and cooperate for the good of the country than it is for the exasperated socialists on the other side of the chamber.